Stress, social support, and racial differences: Dominant drivers of exclusive breastfeeding

Abstract Exclusive breastfeeding is recommended for 6 months; however, many childbearing people wean their infants before 6 months. Psychosocial factors such as stress, social support and race are significant determinants of breastfeeding; however, few studies have longitudinally explored the effect of perceived stress and various forms of social support on exclusive breastfeeding. We used quantitative methodologies to examine exclusive breastfeeding, perceived stress and social support among 251 participants from the Postpartum Mothers Mobile Study. Participants between 18 and 44 years were recruited during pregnancy (irrespective of parity) and completed surveys in real‐time via Ecological Momentary Assessment up to 12 months postpartum from December 2017 to August 2021. We measured perceived stress with the adapted Perceived Stress Scale and perceived social support with the Multi‐dimensional Social Support Scale. Received social support was measured using a single question on breastfeeding support. We conducted a mixed‐effects logistic regression to determine the effect of stress, race and social support on exclusive breastfeeding over 6 months. We examined the moderation effect of perceived social support and breastfeeding support in the relationship between perceived stress and exclusive breastfeeding. Black, compared with White, participants were less likely to breastfeed exclusively for 6 months. Participants who reported higher perceived stress were less likely to breastfeed exclusively for 6 months. Perceived social support moderated the relationship between perceived stress and exclusive breastfeeding (odds ratio: 0.01, 95% confidence interval: 0.001–0.072). However, breastfeeding support directly increased the likelihood of exclusive breastfeeding over 6 months. Perceived stress is negatively associated with exclusive breastfeeding. Birthing people who intend to breastfeed may benefit from perinatal support programs that include components to buffer stress.


| BACKGROUND
Breastfeeding is one of the most significant, cost-effective public health interventions to optimize maternal and child health (Jones et al., 2003;World Health Organization [WHO], 2005). Exclusive breastfeeding for the first 6 months of life is recommended by the WHO and the American Academy of Pediatrics, owing to the dosedependent health and developmental effects of breastfeeding for parents and child (Centers for Disease Control and Prevention [CDC], 2020; Raisler et al., 1999;WHO, 2001). However, most childbearing people in the United States stop breastfeeding or introduce infant formula or complementary foods before 6 months (CDC, 2020).
From the 2018-2019 National Immunization Survey of infants born in 2018 in the United States, 83.9% were ever breastfed (CDC, 2020). This survey also reported that the percentage of infants still breastfeeding at 6 months was 56.7% and 35.0% at 12 months (CDC, 2020). Only 46.3% of children were exclusively breastfed through 3 months, which reduced to 25.8% at 6 months (CDC, 2020).
Comparing infants born in 2018 with those born in 2011, exclusive breastfeeding rates at 3 and 6 months have risen slowly and steadily by 5.6% and 6.6%, (CDC, 2020) likely due to increased breastfeeding promotion efforts (Bibbins-Domingo et al., 2016). However, this increase is not equitably distributed across the United States (Anstey et al., 2017;Geraghty et al., 2012). Among Black infants, 39.3% were exclusively breastfed at 3 months and 19.8% at 6 months, whereas the rates were considerably higher among White infants (i.e., 50.6% for 3 months and 28.8% at 6 months) (CDC, 2020).
Breastfeeding practices are influenced by historical, socioeconomic, cultural, physiological, and psychosocial factors (Rollins et al., 2016;Shiraishi et al., 2020). Sociodemographic factors and maternal characteristics such as age, race/ethnicity, education, employment, income, marital status, perceptions of insufficient milk supply, beliefs, knowledge, attitudes about breastfeeding, and parity have been widely reported as important factors associated with breastfeeding (Bentley et al., 2003;Johnson et al., 2015a;Meyerink & Marquis, 2002). Structural barriers such as suboptimal maternity care practices in birth facilities, lack of workplace breastfeeding support, and predatory advertising from infant formula manufacturers can also influence breastfeeding practices and duration (Johnson et al., 2015a;Rosenberg et al., 2008). In addition, physiological barriers such as unresolved pain can lead to breastfeeding discontinuation (Odom et al., 2013;Shiraishi et al., 2020).
Researchers have also shown that maternal psychosocial factors such as stress and social support are major determinants of breastfeeding (de Jager, Skouteris, et al., 2013;de Jager, Broadbent, et al., 2014;Islam et al., 2017). Maternal stress is associated with adverse perinatal outcomes, including breastfeeding (Ahluwalia et al., 2001;Dole et al., 2003;Mezzacappa, 2004). The relationship between stress and breastfeeding appears complex, and the directionality is unclear (Islam et al., 2021;Nagel et al., 2021;Thome et al., 2006). Experimental studies demonstrate that maternal stress seems to interfere with the release of oxytocin, the hormone responsible for the milk ejection reflex, and if prolonged, can lead to reduced breastmilk production (Dewey, 2001). When going well, breastfeeding is also associated with decreased stress and improved mood among lactating parents (Mezzacappa et al., 2000). This beneficial effect of breastfeeding is said to be mediated by oxytocin and prolactin, hormones necessary for breastfeeding, and is linked to reducing depression and stress (Arletti & Bertolini, 1987;Uvnas-Moberg & Petersson, 2005).
Exposure to stress is common to all; however, in the United States, Black populations are more susceptible to chronic stress, including perinatal stress, compared with White people, which stems from racial discrimination (Dole et al., 2004;Stancil et al., 2000).
Chronic stressors activate the hypothalamic-pituitary-adrenal axis and sympathetic, immune and cardiovascular systems, releasing higher levels of stress hormones such as pro-inflammatory cytokines and cortisol in the effort to restore allostasis (Hawkley et al., 2007;Premji, 2014;Tull et al., 2005). Repeated allostatic responses activated during those stressful situations cause 'wear and tear' to the body and inadvertently lead to allostatic overload (Premji, 2014).
Black populations in the United States have been shown to have a higher allostatic load due to racism, poverty, and perceived stress (Wallace & Harville, 2013). High allostatic load has been posited to contribute to worse health outcomes, including adverse birth outcomes and health risk behaviors such as substance use (Giscombé & Lobel, 2005;Wallace & Harville, 2013).
Social support is one of the essential resources for navigating stressors that can increase substantially postpartum (Islam et al., 2021). Researchers have demonstrated that social support, including from family, friends, peers, and health professionals, is critical to breastfeeding establishment and continuation (Raj & Plichta, 1998). Social support depends on the availability and quality of social relationships, which may moderate stress exposures (Cassel, 1976;Cobb, 1976). This implies that the effect of stress may be more significant among those who lack social ties compared with those who have supportive relationships with others. In a study conducted in Bangladesh, maternal stress negatively influenced exclusive breastfeeding, whereas social support buffered the relationship (Islam et al., 2021). Other studies have found no significant relationship between stress, social support and exclusive breastfeeding (Akman et al., 2008;Jalal et al., 2017).

Key messages
• Childbearing people who reported higher perceived stress were less likely to breastfeed exclusively.
• Perceived social support moderated perceived stress, thereby increasing the likelihood of exclusive breastfeeding.
• Received social support did not moderate perceived stress; however, it directly increased the likelihood of exclusive breastfeeding.
• Overall, Black childbearing people in our study were less likely to exclusively breastfeed.
Researchers have described the relationship between social support and well-being using either the main-effect or buffering models (Cohen & Wills, 1985). The main-effect model suggests that social support produces direct and beneficial effects on well-being, independent of stressors. Alternatively, the buffering model asserts that social support protects individuals by mitigating the adverse effects of stressors (Cohen & Wills, 1985). This has led to categorizing social support into two major types: perceived and received social support (Berkman & Syme, 1979;Helgeson, 1993;Vangelisti, 2009). Perceived social support assesses the extent to which people believe support is available to them, whereas received support assesses specific supportive acts that have occurred (Helgeson, 1993).
Previously, researchers have examined how the two types of social support might impact health. Several studies posit that the perception of support is associated with reduced mortality and seems to be a better predictor of health outcomes than the actual receipt of support (Cohen & Hoberman, 1983;Cohen & Wills, 1985;Eagle et al., 2018;Hartley & Coffee, 2019;Wethington & Kessler, 1986). In contrast, other studies have shown that received support has a more significant effect than perceived support following a stressful event, especially if a single stressor is examined and the support is specific to the stressor (Dunkel-schetter & Bennett, 1990). The conflicting evidence makes health intervention challenging. The distinction between perceived and received social support in the relationship between stress and exclusive breastfeeding is limited.
To date, studies examining the relationship between stress and exclusive breastfeeding have been cross-sectional (Dozier et al., 2012;Dugat et al., 2019) and, as such, the temporal association between stress and breastfeeding patterns cannot be established. Some of these studies had insufficient statistical power (Mezzacappa, 2004) or measured stressful life events (i.e., financial, emotional, traumatic, and partner-associated) but not perceived stress (Dozier et al., 2012;Dugat et al., 2019). Others have focused on a particular group, such as low-income childbearing people (Dozier et al., 2012). Notably, measuring individual stress through stressful life events is complex because of the lack of consistency in its definition (Epel et al., 2018).
In addition, no published study has demonstrated the role of perceived or received social support in the relationship between perceived stress and exclusive breastfeeding using temporal methods, such as the Ecological Momentary Assessment (EMA).
Our objective, therefore, is to examine the relationship between perceived stress and exclusive breastfeeding, and the moderating effects of perceived and received social support on this relationship. In addition, we examined the racial differences in exclusive breastfeeding.

| Study design
Postpartum Mothers Mobile Study (PMOMS) is a longitudinal study designed to understand the contextual, behavioral, psychosocial, and clinical factors related to racial disparities in postpartum weight and cardiometabolic health Mendez et al., 2019Mendez et al., , 2020. It is an ancillary study to the Comparison of Two Screening Strategies for Gestational Diabetes (GDM-2) (Abebe et al., 2017), a randomized controlled trial conducted in a single birthing hospital in Southwestern Pennsylvania.
The GDM-2 study began recruitment in 2015 and required two study visits. Starting in December 2017, participants were approached at these visits, screened and enrolled in PMOMS Mendez et al., 2019Mendez et al., , 2020

| Data collection
EMA via mobile device/smartphone was the primary data collection method for PMOMS (Mendez et al., 2019). EMA data collection occurs in real-time and participants complete surveys capturing momentary states, behavior, and conditions multiple times or as repeated measures (Lazarides et al., 2020, Shiffman et al., 2008. EMA as a data collection method minimizes recall bias, which is common in most retrospective studies (Shiffman et al., 2008).
Participants in PMOMS received text message prompts and completed daily EMA surveys via a mobile phone app at the beginning of day (BOD), end of day (EOD), and random times throughout the day. Participants were allowed to select when to complete the BOD and the EOD surveys with at least 9 hours between these two surveys. Participants received random EMA surveys 0-3 times per day between the BOD and EOD survey times, targeting a mean of 1 random assessment per day over a 7-day period beginning at recruitment (

| Perceived stress
The random EMA measure of stress was adapted from the Perceived Stress Scale (PSS) 10 and 4 (Cohen, Kamarck et al., 1983;Cohen, 1988); we used three items from the Cohen's PSS4 and one item from PSS10. Cronbach α for PSS10 and PSS4 are 0.78 and 0.60, respectively (Lee, 2012). PSS 4 and 10 have been used among Black postpartum people in the United States and validated among perinatal populations (Karam et al., 2012;Thibeau et al., 2016).
Random EMA prompts to assess perceived stress with the adapted PSS instrument were delivered 0-3 times per day, targeting a mean of one random assessment per day over a 7-day period between 18 and 36 weeks pregnancy and 12 months postpartum (Mendez et al., 2019). We used the PSS as a continuous variable to determine the degree to which participants appraise situations in their lives as stressful, uncontrollable, unpredictable and difficult. The items were scored on a 5-point Likert scale, with responses ranging from never (0) to a lot (4).

| Perceived social support
Perceived social support was measured using the MSPSS (Zimet et al., 1988). The MSPSS was measured at one point in time as a non-EMA measure at 12 months postpartum. MSPSS has three subscales that measure an individual's perception of support from three sources: family, friends, and significant other. The widely validated MSPSS scale has 12 items and a Cronbach's α of 0.88; however, we used 11 items to reduce survey burden on the respondents. On a 4-point Likert scale, the respondents indicated the extent to which each statement described their current relationships with their friends, family and significant other.

| Received social support (breastfeeding support)
To measure received social support specifically for breastfeeding, participants completed a single investigator-created item measuring received breastfeeding support. Participants received random prompts in the day asking them about the breastfeeding support they received while breastfeeding. The question was, 'Is there a person/group/organization (e.g., family, professionals) that is helping you or providing any support (e.g., resources, emotional) to continue to breastfeed?' Responses were either 'Yes' or 'No'.

| Statistical analyses
We calculated the internal consistency of the adapted Cohen Perceived scale and the MSPSS using Cronbach's α. We conducted a descriptive analysis of the demographic characteristics of participants and generated individual panel plots for repeated measures of exclusive breastfeeding and perceived stress. We also tested for multicollinearity among the sociodemographic factors and the independent variables. All independent and sociodemographic variables were included since their variance inflation factors were <5.
To examine the relationship between exclusive breastfeeding (a dichotomous variable), perceived stress and social support, we conducted a mixed-effects logistic regression model with random intercepts and unstructured covariance matrices to address clustering of individual responses (panel-data regression). This approach allowed each subject to deviate from the overall mean response by a person-specific constant that applies equally over time. First, we identified covariates included in the final model by conducting a bivariate test of association between exclusive breastfeeding and sociodemographic factors, and independent variables. Next, we specified a null and two full models with random intercepts.
We examined the moderation effect of the two forms of social support (i.e., multidimensional scale of social support and breastfeeding social support) considered perceived and received support, respectively, on perceived stress. In addition, we also examined the moderation effect of race on perceived stress. Model 1 included an interaction term between perceived social support and perceived stress, whereas Model 2 included an interaction term between received social support and perceived stress. We graphically illustrated the interaction between the two forms of social support and perceived stress using the marginplot command in STATA. We used log-likelihood, Bayesian Information  4.5 | Moderating effects of perceived social support and received social support (breastfeeding support) on stress CI: 1.52-3.49). The interaction between perceived social support and stress is presented in Figure 1a. In Figure 1a, there was no remarkable difference in exclusive breastfeeding among individuals who perceived or did not perceive social support for participants with perceived stress score of zero (0). However, as the stress scores increased, those who perceived they had social support were more likely to report exclusive breastfeeding than those who did not perceive social support.

| Interaction effect between race and stress
In Models 1 and 2, examining the interaction terms between stress and race, White participants with similar levels

| Measures of variation
The null model (Model 0), Model 1 and Model 2 have high intraclass correlation (ICC) of 0.91, 0.89, and 0.88, respectively, implying good reliability in individual responses for exclusive breastfeeding. The observed ICC also indicates that the proportion of the total variance observed in our outcome, exclusive breastfeeding due to mean differences between subjects is high.
We further calculated the proportional change in variance, which estimates the total variance attributable to the independent variables in the models. In the perceived social support model (Model 1), only 5% of the observed variation can be attributed to perceived stress, perceived social support and sociodemographic factors. In addition, 14% of the total variance observed in the received social support model (Model 2) was accounted for by received stress, perceived social support and sociodemographic factors.

| DISCUSSION
The primary objective of this study was to examine the influence of perceived daily stress on exclusive breastfeeding. In addition to establishing the relationship between perceived stress and exclusive breastfeeding over 6 months, we sought to test whether perceived social support and received social (breastfeeding) support moderate this relationship. Furthermore, we tested the moderation effect of race on perceived stress. A key finding in the study is that participants who reported higher levels of perceived stress were less likely to breastfeed exclusively for 6 months. Our study results also show that the perception of social support moderated the relationship between perceived stress and breastfeeding. In contrast, challenging. Despite methodological differences, our results corroborate studies that highlighted the influence of stress on exclusive breastfeeding (Dozier et al., 2012;Dugat et al., 2019). Although these studies operationalized stress as stressful life events rather than perceived stress, they demonstrated a significant relationship between stressful life events and decreased likelihood of exclusive breastfeeding. Others have cited possible reasons for the negative relationship between perceived stress and exclusive breastfeeding.
Some researchers posit that elevated stress may induce hormonal responses that can reduce prolactin and oxytocin secretion, leading to inadequate milk supply or preventing the milk letdown reflex, thus causing exclusive breastfeeding cessation (Jalal et al., 2017;Mezzacappa et al., 2000;Mezzacappa, 2004;O'Brien et al., 2008).
An alternative explanation from a recent prospective cohort study in Japan suggests that stress negatively affects exclusive breastfeeding through psychological burden and associated behavioral changes (Shiraishi et al., 2020). Exclusive breastfeeding can be labor-intensive, at times fraught with negative emotions. It is possible that people experiencing stress from other things outside of breastfeeding may seek to decrease additional stress from exclusive breastfeeding. Our findings reinforce mounting evidence that perceived stress is significantly associated with nonexclusive breastfeeding.
In our study, participants who experienced higher stress levels but also perceived social support were more likely to breastfeed exclusively, compared with their counterparts without perceived social support. This finding is consistent with studies that have demonstrated the role of perceived social support from family, friends, and significant others in moderating the effect of stress on health behavior (Allgöwer et al., 2001;Brennan & Moos, 1992;Steptoe et al., 1996). Similarly, several studies have shown that partners, friends and family members provide psychological support, which may not necessarily be breastfeeding support needed to sustain exclusive breastfeeding (Bai et al., 2010;Bevan & Brown, 2014;Brand et al., 2011;Maleki-Saghooni et al., 2020;Ogbo et al., 2020). This relationship can be linked to assertions that childbearing people who perceive they have social support from important persons in their lives adapt better to the postpartum period and cope with stress better in this period (Faridvand et al., 2017) all of which can lead to increased exclusive breastfeeding (Maleki-Saghooni et al., 2020).
In contrast to the buffering role of perceived social support on participants with elevated perceived stress scores, receipt of breastfeeding support as reported by our study participants did not buffer their perceived stress. However, it directly increased the likelihood of exclusive breastfeeding among our study participants.
This finding is similar to previous studies that showed that parents who received social support from health professionals, family, antenatal groups or postpartum breastfeeding support groups have increased breastfeeding self-efficacy and, in turn, exclusively breastfed longer (Brown & Lee, 2011;Laugen et al., 2016;Mercan & Tari Selcuk, 2021). Breastfeeding is a learned behavior (Volk, 2009), and childbearing people can learn to breastfeed from lactation support providers. Learning to breastfeed can improve breastfeeding efficacy, which would increase exclusive breastfeeding. In addition, the receipt of breastfeeding support can directly solve practical problems that could lead to breastfeeding cessation (e.g., identification and treatment of mastitis, treatment for nipple pain/damage, etc.). As shown in our study, breastfeeding support such as support from health care professionals and lactation consultants may not necessarily buffer general stress, especially if the stress is not specific to the postpartum period and breastfeeding.
Childbearing people in our study were significantly less likely to exclusively breastfeed when compared with their White counterparts. Our finding confirms previous studies that have highlighted the racial gap and disparity in breastfeeding indices in the United States (Anstey et al., 2017;Beauregard et al., 2019;Jones et al., 2015).
Black/African Americans have the lowest breastfeeding initiation rates, exclusive breastfeeding and breastfeeding duration than all other racial/ethnic groups. Researchers have also suggested that the long-standing racial and ethnic differences in breastfeeding duration and exclusivity result from historical, cultural, social, economic, political, and psychosocial factors, including stress, which disproportionately affects Black birthing people (Jones et al., 2015;Louis-Jacques et al., 2017;Troxel et al., 2003).
We hypothesized that Black participants who experienced high stress levels will less likely exclusively breastfeed than White This was also necessary to reduce respondent burden and fatigue.
Another limitation is that the MSPSS was administered only once during the study as the participant is exiting the survey, unlike other variables measured repeatedly to reduce respondent burden. We believe, however, that the perception of social support should not fluctuate substantially during this time period. A longitudinal validity (test-retest) of MSPSS scale conducted in a study provides evidence of the scale's stability over time (Dambi et al., 2018;Saeieh et al., 2017). In a study among postpartum mothers, perceived social support was stable for a period of 15 weeks (Saeieh et al., 2017). We also note that our sample was drawn from one county served by one maternity hospital in Pennsylvania, and as such, our findings may not be generalizable to other settings.

| IMPLICATION FOR PRACTICE
To our knowledge, this study is the first longitudinal study to examine how different forms of social support and perceived stress influence exclusive breastfeeding. Our study suggests that perceived stress, perceived social support and receipt of breastfeeding support are important drivers of exclusive breastfeeding. Structural issues including unpaid maternity leave and racism are major sources of stress among birthing people (Troxel et al., 2003) and it is necessary to address these issues among birthing people. In many cases, stress could likely be reduced if parents had extended paid leave, easy access to breastfeeding support in hospital and after discharge, and access to racially concordant care from birth workers ( In addition, maternal stress reduction interventions such as prevention of breastfeeding complications, prenatal lactation counseling, preparation, especially among new parents and relaxation therapy to induce milk production during breastfeeding are effective interventions that can be explored (Shukri et al., 2018).
Our findings substantiate the need for breastfeeding interventions that can improve social support and maximize the use of birthing people's existing social networks. One potential intervention that can be scaled up is the use of racially diverse Community Health Workers (CHWs) as breastfeeding peer counselors providing culturally and linguistically appropriate breastfeeding counseling and support services. The engagement of these CHWs in home visiting programs is a proven way to promote and support breastfeeding (Chapman et al., 2010). CHWs are uniquely positioned to address racial health disparities that disproportionately affect communities of color. Expanding their scope to provide breastfeeding services can help reduce structural barriers to breastfeeding such as access to information and services Black birthing people face.
In addition, the scope of work for Doulas can be expanded to provide breastfeeding support services. We also recommend that public health program implementers design breastfeeding support programs involving partners, family and friends, as these individuals play an important role in buffering stress, especially among minority groups. Further studies are needed to determine the potential sources of stress among breastfeeding people and how different types of social support, such as emotional, informational, appraisal and tangible support, will affect exclusive breastfeeding.